By now I have the managed to implement the .vmx -> .xml part.
According to "General tips for contributing patches" (http://libvirt.org/hacking.html#patches)
I am sending the patch back to the community as early as it has
sense as I still hope to contribute this feature to the community.
It builds and has been functionally tested. I also tried my best to
stick to coding conventions applied on the project. So I hope my
patch will not take long time to analyze for someone experienced
enough.

I saw someone already has started (put few comments about snapshot
modes in src/vmx/vmx.c). So tried to undestand an original idea and
keep up with it. I hope I was not wrong there.

I am willing to keep working in this direction. So if someone would
be so kind to take a look at my efforts and provide a feedback - it
would be very nice and, I hope, useful for the rest of the project.